1. Field of the Invention
The invention relates to a silent chain wound on a pair of sprockets that are apart from each other to transmit power from a drive sprocket to a follower sprocket.
2. Prior Art
A silent chain is a chain wound on a pair of sprockets that are apart from each other to transmit power from a drive sprocket to a follower sprocket. For example, the silent chain disclosed in U.S. Pat. No. 5,989,141 is one in which a link row that consists of a pair of guide plates and a number N of link plates and a link row that consists of a number N+1 of link plates are connected to one another by connection pins and arranged in alternating sequence in an endless loop.
In the silent chain described in the foregoing patent, the link plates in the link row including the guide plates are thin and some of the link plates in the link row that does not include the guide plates are thicker in order to balance the tensile strengths of the link rows.
A first problem is that strength of the link row including the guide plates is different from the strength of the link row that does not include the guide plates.
In the link row which includes guide plates in addition to link plates, the guide plates also bear a part of the load applied to the silent chain. The link row that does not include guide plates bears the load applied to the silent chain only through its link plates. For this reason, it is extremely difficult to make the strengths of the link rows uniform.
A second problem is that a that pitches of the link row including the guide plates and the link row that does not include guide plates easily become different from each other.
If the silent chain does not adopt the invention described in U.S. Pat. No. 5,989,141, but all link plates are the same, the strength of the link row including the guide plates increases, and elongation of the link row including the guide plates becomes smaller compared to elongation of the link row that does not include the guide plates.
Since load balance is taken into consideration in the silent chain that adopts the invention described in the different link rows become closer to a certain extent. However, elongation of the link row is caused by: (1) flexure of pin; (2) load and stress applied to the link plate; (3) load and stress applied to the guide plate; (4) deformation of the guide plate; (5) plastic deformation between pin and pin hole when a proof load is applied; or the like. Therefore, if a configuration of the link row is different, the pitch itself easily becomes different, and the change of pitch is also different when a load is applied.
If the pitch and its change are different in each link row, conditions for engagement with the sprocket are also different in each link row. When the conditions for engagement are different in each link row, problems such as engagement failure and noise occur. Such problems cause adverse effect to the life of entire silent chain.
A third problem is that two or more kinds of link plates must be controlled and assembled correctly.
The length, the height and the thickness of a small link plate are approximately 12 mm, approximately 7 mm and approximately 1 mm respectively. The thickness difference between link plates which have different thickness is approximately 0.4 mm. It is extremely difficult to recognize the thickness difference by visual inspection at the site of mass production. Accordingly, although accurate parts control is used to prevent mixture of different link plates, parts control is not easy. Further, since different link plates are assembled in a link, assembly is laborious and quite uneconomical.
An object of the invention is to provide a silent chain in which configurations of link rows are made uniform to make the strengths of the link rows equal.
Another object of the invention is to provide a silent chain in which elongation of the links is made equal regardless of elastic deformation and/or plastic deformation.
Still another object of the invention is to provide a silent chain in which the number of parts is reduced to reduce a production cost.
The invention has solved the foregoing problems by a silent chain that includes:
a first link row that consists of one guide plate and a number N of link plates;
a second link row that consists of one guide plate and a number N of link plates; and
a connection pin, and in which the guide plates of the first link row and the second link row are of the same shape and size, the link plates of the first link row and the second link row are of the same shape and size, the first link row and the second link row are arranged in staggered arrangement along the longitudinal direction of the chain and connected in alternating, interleaving relationship on the connection pin, and the guide plates and the link plates of the first link row and the second link row are relatively rotatable on the connection pin.
In the silent chain of the invention composed as described above, a guide plate at one side of a first link row spans the outermost link plates of the two adjacent second link rows, and no guide plate is provided at the other side of the first link row. Conversely, a guide plate at one side of a second link row spans the outermost link plates of the two adjacent first link rows, and no guide plate is provided at the other side of the second link row. Therefore, there is only one guide plate for each link row, and the guide plates are in a staggered arrangement along the longitudinal direction of chain.
The configuration of each link row is the same. Specifically, each link row consists of a guide plate and a number of link plates, the guide plates are of the same shape and size, the link plates are of the same shape and size, and the number of link plates in each link row is the same as the number of link plates in every other link row. The guide plate and the link plates of each link row are rotatable on each connection pin.
Accordingly, since the load applied to each link row is the same, the load and the stress applied to the guide plate of the first link row and the guide plate of the second link row are the same. Further, the load and the stress applied to the link plate closest to the guide plate of the first link row and the link plate closest to the guide plate of the second link row are the same. Moreover, the first and second link rows have the same load and stress applied to the other link plates. Because the link rows are composed as described above, the first and second link rows have the same strength.
As in the foregoing, since the load and the stress applied to each guide plate are the same, and the load and the stress applied to each link plate are the same, the elongation of the guide plates and the link plates is also the same regardless of elastic deformation and/or the plastic deformation. The same elongation in the first and second rows causes the pitch to remain the same for each link row, even if the pitch changes.
In other words, the strength and the elongation of each link row are made uniform in the silent chain of the invention. Accordingly, all the link rows are engaged with the sprocket under the same conditions.